/*

 * Copyright (c) 2020, Ali Mohammad Pur <mpfard@serenityos.org>

 * Copyright (c) 2022, the SerenityOS developers.

 *

 * SPDX-License-Identifier: BSD-2-Clause

 */

#pragma once

#include <AK/Optional.h>

#include <AK/Span.h>

#include <AK/Types.h>

namespace Crypto::Cipher {

enum class Intent {

    Encryption,

    Decryption,

};

enum class PaddingMode {

    CMS,     // RFC 1423

    RFC5246, // very similar to CMS, but filled with |length - 1|, instead of |length|

    Null,

    ZeroLength,

    // FIXME: We do not implement these yet

    Bit,

    Random,

    Space,

};

bool padding_always_needs_extra_block(PaddingMode);

template<typename B, typename T>

class Cipher;

struct CipherBlock {

public:

    explicit CipherBlock(PaddingMode mode)

        : m_padding_mode(mode)

    {

    }

    virtual ReadonlyBytes bytes() const = 0;

    virtual void overwrite(ReadonlyBytes) = 0;

    virtual void overwrite(u8 const* data, size_t size) { overwrite({ data, size }); }

    virtual void apply_initialization_vector(ReadonlyBytes ivec) = 0;

    PaddingMode padding_mode() const { return m_padding_mode; }

    void set_padding_mode(PaddingMode mode) { m_padding_mode = mode; }

    template<typename T>

    void put(size_t offset, T value)

    {

        VERIFY(offset + sizeof(T) <= bytes().size());

        auto* ptr = bytes().offset_pointer(offset);

        auto index { 0 };

        VERIFY(sizeof(T) <= 4);

        if constexpr (sizeof(T) > 3)

            ptr[index++] = (u8)(value >> 24);

        if constexpr (sizeof(T) > 2)

            ptr[index++] = (u8)(value >> 16);

        if constexpr (sizeof(T) > 1)

            ptr[index++] = (u8)(value >> 8);

        ptr[index] = (u8)value;

    }

protected:

    virtual ~CipherBlock() = default;

private:

    virtual Bytes bytes() = 0;

    PaddingMode m_padding_mode;

};

struct CipherKey {

    virtual ReadonlyBytes bytes() const = 0;

    static bool is_valid_key_size(size_t) { return false; }

    virtual ~CipherKey() = default;

protected:

    virtual void expand_encrypt_key(ReadonlyBytes user_key, size_t bits) = 0;

    virtual void expand_decrypt_key(ReadonlyBytes user_key, size_t bits) = 0;

    size_t bits { 0 };

};

template<typename KeyT = CipherKey, typename BlockT = CipherBlock>

class Cipher {

public:

    using KeyType = KeyT;

    using BlockType = BlockT;

    explicit Cipher(PaddingMode mode)

        : m_padding_mode(mode)

    {

    }

    virtual KeyType const& key() const = 0;

    virtual KeyType& key() = 0;

    constexpr static size_t block_size() { return BlockType::block_size(); }

    PaddingMode padding_mode() const { return m_padding_mode; }

    virtual void encrypt_block(BlockType const& in, BlockType& out) = 0;

    virtual void decrypt_block(BlockType const& in, BlockType& out) = 0;

#ifndef KERNEL

    virtual ByteString class_name() const = 0;

#endif

protected:

    virtual ~Cipher() = default;

private:

    PaddingMode m_padding_mode;

};

}